Drill bit



United States Patent Charles R. Frederick Houston, Texas Feb. 28, 1969 Oct. 20, 1970 G. W. Murphy Industries, Inc. Houston, Texas a corporation of Texas Inventor Appl. No. Filed Patented Assignee DRILL BIT 10 Claims, 8 Drawing Figs.

US. Cl 175/337 Int. Cl E2lc 13/00 Field otSearch 175/337,

Primary Examiner-David H. Brown Attorney-l Vincent Martin, Joe E. Edwards and Jack R.

Springgate ABSTRACT: An improved drill bit having a gaseous circulation system for the roller cutters to be used in gas drilling so that a portion of the gas which is circulated through the drill is circulated through the roller cutters to cool the cutter bearings.

Patented Oct. 20, 1970 Sheet (flaw/e: R. Freda/v04 INVENTOR.

Patented Oct. 20, 1970 3,534,823

(flaw/e: R fiea er/c/r INVENTOR.

ATTORNEVJ DRILL BIT SUMMARY The present invention relates to an improved drill bit for use in drilling with a gaseous circulating fluid.

Prior drill bits having air or gas circulation have not had seals but have caused the air circulation to flow through the bearing. With such drill bits, when water is encountered or is injected for dust control, the heavier moist cuttings often are forced into the bearings which results in a relatively short bearing life. Other types of bits having seals are not satisfactory since the seals are exposed and once they are destroyed, the bearings deteriorate rapidly with the entry of the cutting into the bearings.

An object of the present invention is to provide an improved drill bit for use in drilling with air or gas circulation which bit has extended life and improved bit footage.

A further object is to provide an improved roller cutter drill bit with a circulation system to extend the life of the cutter seals.

Still another object is to provide an improved roller cutter drill bit with a circulation system utilizing the ball loading hole and in which gas circulated therethrough cools the roller cutter to extend its bearing life.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a sectional view of one segment of a drill bit taken along line 1-1 in FIG. 2 to illustrate the inlet passages of the circulation system of the present invention.

FIG. 2 is an internal view of a segment of the improved drill bit of the present invention with the roller cutter removed.

FIG. 3 is a sectional view taken along line 3-3 in FIG. 2 to show a portion of the outlet passages of the circulation system of the present invention.

FIG. 4 is a sectional view taken along line 4-4 in FIG. 3 showing the discharge passage.

FIG. 5 is a sectional view taken along line 5-5 in FIG. 3 showing the relationship of the outlet passages.

FIG. 6 is a sectional view of a drill bit segment illustrating a modified form of circulating system.

FIG. 7 is a sectional view taken along line 7-7 in FIG. 6 showing the passages in the bearing shaft and the discharge passage.

FIG. 8 is a perspective view of the modified ball loading plug shown in FIGS. 6 and 7.

DESCRIPTION OF THE PREFERRED EMBODIMENT In the drawings, the drill bits are shown by showing details of one segment, it being understood that the drill bit will normally have two or more segments. The drill bit segment 10 as shown in FIGS. 1 and 2 includes the leg 12 depending from the head or body 14. The head 14 defines the internal chamber 16 which during drilling is in communication with the circulating fluid passage in a drill string when the drill bit is connected to the lower end of the drill string for drilling. The leg 12 terminates in the bearing shaft 18.

The roller cutter 20 is mounted on bearing shaft 18 and the bearing means including the roller bearings 22 and the ball bearings 24 are provided to support the roller cutter 20 for rotation about bearing shaft 18. From FIG. 1 it can be seen that bearing shaft 18 defines the roller race 26 and the ball race 28 while the cutter 20 defines the mating roller race 30 and the ball race 32. To prevent the entry of solids between the cutter 20 and the bearing shaft 18 the annular seal 34 is positioned to seal between the open end of cutter 20 and the bearing shaft 18. As long as seal 34 functions properly, the bearings 22 and 24 are protected from solids.

In order to prolong the life of seal 34 and to cool bearings 22 and 24, the drilling fluid (gas or air), is circulated through the space between roller cutter 20 and bearing shaft 18. The

inlet passages 36 and 38 are located in leg 12 and bearing shaft 18 as shown and provide communication from chamber 16 to the space between the annular shoulder 40 on bearing shaft 18 and the shoulder 42 defined in cutter 20. Passage 44 communicates from passage 38 to the bearing race 28. As best seen in FIG. 2 a portion of shoulder 40 around the opening of passage 38 is removed providing recess 39 to minimize the restriction to the flow of fluid discharged from passage 38.

The return flow of fluid is directed through passages 46 and 48 into the ball loading hole 50 and is discharged from the drill bit segment 10 through the passage 52 which communicates from the ball loading hole 50 through check valve 53 to the trailing side of leg 12. As shown in FIGS. 3, 4 and 5, the plug 54 is positioned in the ball loading hole 50 to retain the balls in their races. The intermediate portion of plug 54 has a reduced diameter to provide communication from passages 46 and 48 through the ball loading hole 50 to the outlet passage 52 which opens to the exterior trailing side of leg 12 to prevent clogging of the passages. Passage 46 communicates between the recess 56 in the end of bearing shaft 18 to the ball loading hole 50. Passage 48 communicates from the roller race 26 to the ball loading hole 50.

The passages shown and described provide for circulation I of the gaseous drilling fluid through and over the bearing surfaces to cool the points of rolling and sliding contact between bearing shaft 18 and roller cutter 20. It has been found that this cooling extends the life of the seal 34 and consequently by preventing entry of solids into the bearings extends the life of the cutter.

In the modified form of the invention illustrated in FIGS. 6, 7 and 8, the same type of passages are provided to deliver the air or gaseous drilling fluid to cool the bearings. In this modified form all components which are the same as shown in the other drawings are given the same number.

The ball loading hole 50 in this modified form is used for both an inlet passage and an outlet passage. To accomplish this dual use of the ball loading hole 50, the special plug 58 is provided. As shown, plug 58 includes the bearing support 60 and the outer cylindrical end 62 joined by the flat arm 64. Arm 64 has a width which is substantially the diameter of the ball loading hole 50 so that it will seal against the interior of hole 50 or restrict the flow of fluid directly between its inlet and outlet sides.

Inlet passage 66 extends from chamber 16 to the inlet side of loading hole 50. Passage 68 communicates from the inlet side of hole 50 to the recess 70 in the outer end of bearing shaft 18. Passage 72 communicates between bearing race 26 and the outlet side of arm 64 in hole 50. Passage 74 communicates from the outlet side of hole 50 to discharge fluid on the trailing side of drill bit segment 10.

Fluid from chamber 16 is thus circulated through passage 66, the inlet side of hole 50 and passage 68 to the end of bearing shaft 18 within cutter 20. The fluid flows over contact surfaces to cool such surfaces and is discharged through passage 72, the outlet side of hole 50 and passage 74 to the exterior of the drill bit.

Both forms of the present invention provide for the circulation of a gaseous drilling fluid over the contact surfaces between the roller cutter and the bearing shaft and discharge the fluid therefrom. This fluid flow cools the bearing surfaces to extend the life of the cutter seal, thus extending the life of the cutter. In both forms of the invention, passages are provided to direct fluid to and discharge fluid from the space between the roller cutter and the bearing shaft. The ball loading hole is used as a passage in both forms. In the modified form by providing a special plug it is used for the dual function a head defining an internal chamber;

a leg depending from said head;

said leg terminating in a bearing shaft;

a roller cutter adapted to be mounted on said bearing shaft;

bearing means supporting said roller cutter for rotation about said bearing shaft;

a seal positioned between the open end of said cutter and said shaft to prevent entry of solids to said bearing means between said roller cutter and said shaft;

a first passage through said leg and said bearing shaft communicating from said internal chamber to a position between said shaft and said cutter; and

a second passage extending through said shaft and said leg communicating from a position between said shaft and said cutter and spaced from said aforementioned position to the exterior of said leg whereby a portion of the fluid being circulated through said internal chamber is circulated through said first passage, between said shaft and said cutter, and through said second passage to cool said cutter and said shaft.

2. A drill bit according to claim 1. wherein:

said first passage communicates with at least two spaced apart positions between said roller cutter and said bearing shaft; and

said second passage communicates with at least one position between said roller cutter and said bearing shaft spaced from both of said positions of said first passage.

3. A drill bit according to claim 1, wherein:

said bearing means includes ball bearings and roller bearings; and

said passages are positioned to cause flow over said ball bearings and said roller bearings.

4. A drill bit according to claim 1, wherein:

said second passage communicates with the exterior of said leg on the trailing side thereof.

5. A drill bit according to claim 4, including:

a check valve positioned in said second passage to prevent flow through said second passage toward said bearing means.

6. A drill bit according to claim 1, wherein:

said bearing means includes ball bearings;

said bearing shaft defines a ball loading hole;

a plug positioned in said ball loading hole; and

a portion of said ball loading hole providing a portion of at least one of said passages.

7. A drill bit according to claim 6. wherein:

said plug has a reduced intermediate portion to provide space within said ball loading hole 'for flow of fluid therethrough. I I

8. A drill bit according to claim 6, whereiriza portion of said ball loading hole provides a portion of each of said passages.

9. A drill bit according to claim 8, wherein:

said plug has a flattened intermediate portion dividing said ball loading hole into an inlet portion forming a portion of said first passage and an outlet portion forming a portion of said second passage.

10. A drill bit comprising:

a body;

a bearing shaft supported from the body;

a roller cutter adapted to be rotatively mounted on said bearing shaft;

bearing means supporting said cutter on said bearing shaft;

a chamber within said body and adapted to be in communication with the drilling fluid passage in a drill string when said drill bit is connected to the drill string; and

a plurality of passages communicating from said chamber to a first position between the bearing shaft and said cutter and from a second position between said bearing shaft and said cutter through said shaft and said body to the exterior of said body whereby drilling fluid is circulated through the space between said cutter and said bearing shaft. 

